1. Field of the Invention
The present invention relates to a knife apparatus including a knife handle or grip having a substantially C-shaped cross-section defining a groove or a channel extending longitudinally thereof and a slide unit having a blade secured thereto and slidably received by the channel so that the blade can be withdrawn or projected bit by bit outwardly as the knife edge thereof wears out.
2. Description of the Prior Art
In the knife apparatus of the type described above, it has been hitherto known that a series of notches or teeth are formed in the knife handle or grip along the groove on one hand, while a V-shaped spring member is mounted on the slide unit on the other hand, whereby the slide unit and hence the blade are securely held by the knife handle through the mutual engagement of the V-shaped spring and the notch. When the slide unit is moved to project the blade outwardly, the V-shaped spring is yieldably deformed to disengage from the notch. Such conventional structure is, however, disadvantageous in that the blade can not be securely held by the knife handle or grip at the indexed position since the locked or latched state of the slide unit is assured only by the resiliency of the V-shaped spring member. Consequently, there may arise a danger of the blade tottering or rattling particularly in the applications where a relatively great cutting force is required. Of course, more positive locking of the slide unit as well as the blade to the knife handle may be attained by using a spring member having a correspondingly increased spring force. However, by doing so, the force required for smoothly sliding the slide unit is increased inconveniently.
To avoid this problem, there have been proposed various knife apparatus having means for releasably but forcibly keeping the V-shaped spring in engagement with the notch. However, with all these means, it was still difficult to rigidly smoothly lock the blade at an indexed position with a simple, smooth manipulation. Also, it was difficult to assure sufficient strength and easy manufacture of the knife apparatus. Such problem becomes remarkable particularly in the knife apparatus in which a blade of a small width is to be incorporated.